The broad objective of the proposed research project is to gain a more complete understanding of cancer. Our unique animal models for the study of teratocarcinogenesis in the mouse testis and ovary will enable us to combine developmental and genetic approaches. Recently developed methods and genetically controlled mammalian materials will make it possible to investigate very early stages in the neoplastic transformation of early embryonic cells, male primordial germ cells, and ovarian oocytes. Subtle genetic and environmental factors determine whether a cell will remain embryonic and proliferate idefinitely like a tumor cell, or whether it will become determined and differentiate into a benign cell. We will investigate the influence of single genes and the X chromosome on teratocarcinogenesis and parthenogenesis. We will create new inbred strains of mice with special characteristics that influence these processes. We will investigate the influence of temperature and laterality on testicular and ovarian teratocarcinogenesis in vitro and in vivo. We will attempt to induce parthenogenesis experimentally within the ovaries and in the oviducts of strain LT/Sy mice. We will define the developmental potencies of embryonal carcinoma cells, and attempt to direct their differentiation. We will investigate the molecular basis for susceptibility to teratocarcinogenesis.